outpacket.java

用java实现的

/*
* LumaQQ - Java QQ Client
*
* Copyright (C) 2004 luma <[e-mail]>
*                    notXX
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.tsinghua.lumaqq.qq.packets;

import java.nio.ByteBuffer;

import edu.tsinghua.lumaqq.qq.Crypter;
import edu.tsinghua.lumaqq.qq.QQ;
import edu.tsinghua.lumaqq.qq.Utils;


/**
 * 发出的包, 是所有发出包的基类.
 * 每一个发出包都有一个头部和一个尾部, 头部的格式为:
 * <ol>
 * <li>头部
 * <ol>
 * <li>标志字节, 0x00. (==0x2)
 * <li>客户端版本代码, 0x01~0x02.
 * <li>命令类型, 0x03~0x04.
 * <li>包序号, 0x05~0x06.
 * </ol>
 * <li>包的内容
 * <li>尾部, 0x00. (==0x3)
 * </ol>
 * 头部, QQ号和尾部都是不加密的, 除此之外内容部分都将用会话密钥加密, 其中登录包要用密码密钥加密
 * 相对基类增加了是否需要重发的属性.
 * 
 * @see notxx.lumaqq.qq.QQ#QQ_PACKET_TAG
 * @see notxx.lumaqq.qq.QQ#QQ_PACKET_TAIL
 * @author notxx
 * @author 马若劼
 */
public abstract class OutPacket extends Packet {
	/** 加密者 */
	protected static final Crypter crypter = new Crypter();
	/** 包起始序列号 */
	protected static char seq = (char) Utils.random().nextInt();
	/** 
	 * 包体缓冲区，有back array，用来存放未加密时的包体，子类应该在putBody方法中
	 * 使用这个缓冲区。使用之前先执行clear() 
	 */
	protected static final ByteBuffer bodyBuf = ByteBuffer.allocate(3000);

	/** 是否需要回应 */
	private boolean ack;
	/** 重发计数器 */
	private int resend;
	/** 超时时间 */
	private long timeout;

	/**
	 * 构造一个参数指定的包.
	 * @param command
	 *                   命令.
	 * @param ack
	 *                   是否需要回应.
	 */
	protected OutPacket(char command, boolean ack) {
		super(QQ.QQ_CLIENT, command, seq++);
		this.ack = ack;
		this.resend = QQ.QQ_ACK_PACKET_SEND_TIME;
	}

	/**
	 * 将整个包转化为字节流, 并写入指定的ByteBuffer对象.
	 * 一般而言, 前后分别需要写入包头部和包尾部.
	 * 
	 * @see OutPacket#putHead(ByteBuffer)
	 * @see OutPacket#putTail(ByteBuffer)
	 * @param buf
	 *                   将包写入的ByteBuffer对象.
	 */
	public void fill(ByteBuffer buf) {
	    // 保存当前pos
	    int pos = buf.position();
	    // 填充头部
	    putHead(buf);
	    // 填充包体
	    bodyBuf.clear();
	    putBody(bodyBuf);
	    bodyBuf.flip();
	    // 加密包体
	    byte[] enc = encryptBody(bodyBuf.array(), 0, bodyBuf.limit());
	    // 加密内容写入最终buf
	    buf.put(enc);
	    // 填充尾部
	    putTail(buf);
	    // 如果是tcp包，到包的开头处填上包长度，然后回到目前的pos
	    if(!user.isUdp()) {
	        int len = buf.position() - pos;
	        buf.putChar(pos, (char)len);
	    }
	}
	
	/**
	 * 加密包体
	 * @param b 未加密的字节数组
	 * @param offset 包体开始的偏移
	 * @param length 包体长度
	 * @return 加密的包体
	 */
	private byte[] encryptBody(byte[] b, int offset, int length) {
	    if(command == QQ.QQ_CMD_LOGIN) {
	        byte[] ret = new byte[length];
	        System.arraycopy(b, offset, ret, 0, length);
	        return ret;
	    } else
	        return crypter.encrypt(b, offset, length, user.getSessionKey());
	}
	
	/**
	 * 将包头部转化为字节流, 写入指定的ByteBuffer对象.
	 * 
	 * @param buf
	 *                   写入的ByteBuffer对象.
	 */
	protected final void putHead(ByteBuffer buf) {
	    if(!user.isUdp())
	        buf.putChar((char)0);
		buf.put(QQ.QQ_PACKET_TAG);
		buf.putChar(source);
		buf.putChar(command);
		buf.putChar(sequence);
		buf.putInt(user.getQqNum());
	}
	
	/**
	 * 初始化包体
	 * @param buf
	 */
	protected abstract void putBody(ByteBuffer buf);
	
	/**
	 * 将包尾部转化为字节流, 写入指定的ByteBuffer对象.
	 * 
	 * @param buf
	 *                   写入的ByteBuffer对象.
	 */
	protected final void putTail(ByteBuffer buf) {
		buf.put(QQ.QQ_PACKET_TAIL);
	}
	
	/**
	 * 是否需要重发.
	 * 
	 * @return 需要重发返回true, 否则返回false.
	 */
	public final boolean needResend() {
		return (resend--) > 0;
	}
	
	/**
	 * @return true表示包需要回复
	 */
	public final boolean needAck() {
	    return ack;
	}
	
    /**
     * @return Returns the timeout.
     */
    public long getTimeout() {
        return timeout;
    }
    
    /**
     * @param timeout The timeout to set.
     */
    public void setTimeout(long timeout) {
        this.timeout = timeout;
    }
}